Asaph Hall, an American astronomer known for his extensive studies of Mars, discovered Phobos, a small moon of the Red Planet, in his observations taken at the United States Naval Observatory in Washington, D.C. Using a large telescope, Hall focused on the planet's movements and its surrounding celestial bodies. His meticulous work led him to identify Phobos on August 18, 1877, marking a significant milestone in the study of Martian moons. He later discovered Deimos, the second moon of Mars, a few days later, on August 12, 1877.

The discovery of Phobos and Deimos transformed scientific understanding of Mars and its companions. Initially suspected to be asteroids, both moons were noted for their irregular shape and size, further propelling the field of lunar studies. Hall's precise calculations also linked these moons' orbits closely to Mars' gravitational influence, indicating that they were captured objects rather than formed from the planet itself.

This finding was acknowledged as a major leap in astronomical discoveries of the time, as it added to the understanding of planetary systems. The study of Phobos and Deimos paved the way for further explorations into the Moons' compositions and helped set the stage for future Mars missions. Years later, both moons would become focal points for space missions due to their connection to Mars and their position within the solar system. Hall's contributions to astronomy extended beyond this discovery and intertwined with the ongoing exploration of Mars throughout the 20th and 21st centuries.